Seasonal variations of the ovarian activity and pregnancy rate in the Egyptian buffalo cows (Bubalus bubalis).

The objective of this study was to investigate the effect of season on the follicular and luteal dynamics and pregnancy rate in Egyptian buffaloes. A total of 327 genital tracts and 596 animals were used. The genital tracts were examined in winter (n = 58), spring (n = 179), summer (n = 49), and autumn (n = 41) for follicular population, incidence of presence of developed or mature corpus luteum (CL), and diameters of the preovulatory follicle (OF) and the mature CL. Buffaloes were mated in winter (n = 297) and summer (n = 299) and examined for pregnancy rate. Results showed that the mean number of the large follicles was higher in winter (1.21 ± 0.08 mm) and spring (1.04 ± 0.05 mm) than in summer (0.64 ± 0.1 mm) and autumn (0.78 ± 0.1 mm) (P = 0.0001). Likewise, the mean diameter of the OF was greater in winter (14.71 ± 0.7 mm) and spring (14.36 ± 0.5 mm) than in summer (12.4 ± 0.8 mm) and autumn (12 ± 0.8 mm) (P = 0.02). In addition, the mean diameter of the mature CL was higher in winter (15.8 ± 0.4 mm) and spring (15.5 ± 1.1 mm) than in summer (14.2 ± 1 mm) and autumn (13.2 ± 0.7 mm) (P = 0.003). The incidence of presence of developed or mature CL was lower in summer (69.4 %) than in winter (74.1 %), spring (87.2 %), or autumn (85.4 %) (P = 0.01). Double CLs (0.9 %) were observed only in spring. Ovarian cysts (2.5 %) were detected in winter and spring. The pregnancy rate was higher in buffaloes mated in winter (75.4 %) than in those mated in summer (61.9 %) (P = 0.0004). In conclusion, season affects the ovarian activity and reproductive efficiency of buffaloes, where winter and spring are the optimum seasons for breeding.